This invention relates to generating epidermis or other coherent epithelia from cultured human cells.
Banks-Schlegel and Green, 29 Transplantation 308, 1980, describe growing human epidermal cells in surface culture by inoculation into medium suspensions of disaggregated cells. These cells grow into colonies and the colonies fuse to form a confluent epithelium which can be detached and transplanted to athymic mice. Specifically, full-thickness skin was removed from athymic animals and the graft was applied to the fascia covering the thoracic wall. Such grafts form epidermis having all cell layers, including a stratum corneum. "Although they become considerably reduced in area, the grafts remain healthy for as long as 108 days after grafting." Id. at 308. However, after 10 days from grafting "no information could be obtained by inspection of the graft because the human epidermis could not be distinguished with certainty from that of the mouse . . . " Id. at 312. Human epidermis was identified using species-specific antiserum and examination of microscopic sections.
Worst et al., 53 J. Nat. Can. Inst. 1061, 1974 and Karasek, 51 J. Invest. Derm. 247, 1968, describe the use of glass or silicone chambers for growing epidermis from implanted epidermal cell cultures. The chambers are inserted under the wound edge after the epidermis and dermis are excised down to the muscle fascia. Such chambers prevent wound contraction but "intense hyperplasia was common in every transplantation site." (Id. at 251. Further, there was "a complete deterioration of the transplanted cells within 6 weeks . . . " Such deterioration may be ". . . a direct consequence of a change in the normal connective tissue environment . . ." Id. at 251. Karasek suggested that such explant cultures "can provide an experimental approach to a study of the factors that affect somatic stability of epithelial cells in cell culture." Id. at 251.
Krueger et al. 5 Fundamental and Applied Toxicology S112, 1985, describe a process of skin grafting in four stages. In the first stage a skin graft is placed inside an epigastric flap of a rat. In later stages, the femoral vessels supplying this graft are isolated, the flap removed through a subdermal tunnel to the dorsal side of the rat, and stitched in place.